---------- *7 (OLD) TOOLS* ---------- THE 7 (OLD) TOOLS FOR PROBLEM-SOLVING IN TOTAL QUALITY CONTROL (TQC) 1. Check Sheet (To Categorize the Customer Causes of Rejection). To promote the collection of purposeful, reliable data by making data easy to obtain and easy to use. Usually used at Inspection Stage to accumulate rejection causes by various types. This answers the question "Why was each item rejected?" Example--Note and accumulate how many defective springs are from pinholes, dimensions, cracking, scratching, other. 2. Pareto Diagram (To Order the Customer Causes of Rejection). To indicate which problem should be solved first to eliminate defects and improve the operation. This orders the causes-of-rejection. Example--the ordering of cause-of-rejection is cracking, scratching, pinholes, dimensions, other. Note what customer cause- of-rejection is most frequent. 3. Cause and Effect Diagram (Fishbone Diagram, Ishikawa Diagram). To relate a selected customer requirement to various measurable product characteristics; also, to relate a selected measurable product characteristic to various input/process/output characteristics. To categorize and enumerate the causes for quality dispersion (4 general categories--material, machine, man, method). It is a useful graphical technique to assist engineering brainstorming to relate a selected requirement/characteristic to various component/product/process characteristics. Example--cracking may be due to input materials, machine, man (shifts), method (assembly process), hardening temperature, quenching temperature, the inspection process itself, the output spring type, etc. 4. Histogram (of Some Primary Product Characteristic). To show the central value, dispersion, and shape of the distribution of measurements from a production line. Example--if cracking is the primary cause of rejection, then examine the distribution of some physical property of cracking, such as length, depth, location, etc. 5. Stratification (of Histograms). Examine the distribution as a function of various factors and levels within factors. Example--compare the distribution of the size of cracks for spring type A with the distribution of size of cracks for spring type B. A bihistogram may be useful. 6. Scatter Diagram. To show the nature of the relationship between 2 kinds of data (variables). This is really more stratification--but by scatter plot rather than by by histogram. Example--how does crack size vary as a function of some continuous variable (such as oven temperature)? 7. Graphs and Charts (including Control Charts). To determine if material, man, machine, and method effect the production output over time, and to determine if the process is statistically "in control". Example--if crack size is related to oven temperature, what does the control chart of temperature reveal in terms of instability & unusual patterns. Source --Total Quality Control (TQC): The Japanese Way. Q. C. Trends, August 1985, pages 9-10. See Also--Box & Bisgaard (1987). The Scientific Context of Quality Improvement. Quality Progress, page 55-56.